There are electric compressors mounted on refrigeration and air-conditioning apparatuses, such as refrigerators and air conditioners, with structures illustrated in FIGS. 1 and 2. FIG. 1 is a schematic explanatory diagram (schematic diagram of a longitudinal section) illustrating an embodiment of an electric compressor mounted on a refrigeration and air-conditioning apparatus. FIG. 2 is a partial schematic explanatory diagram illustrating a stator of a motor component in FIG. 1, in which FIG. 1A is a plan view and FIG. 1B is a side view partially showing a cross sectional view. Note that in FIGS. 1 and 2, a hermetic electric compressor is shown as an embodiment of an electric compressor mounted on a refrigeration and air-conditioning apparatus.
A motor component 2, a compression component 3 that is driven by the motor component 2, and other components are provided in a hermetic vessel 1. Further, refrigerating machine oil 4 is retained in the bottom portion of the hermetic vessel 1.
The motor component 2 includes a stator 21 and a rotor 22. An outer circumference of the stator 21 is fixed to the hermetic vessel 1. A magnet wire 6 provided in the stator 21 is connected to a sealed power terminal 7 provided in the hermetic vessel 1, and is supplied with power from a power source (not shown). The rotor 22 is supported so as to maintain a constant gap with an inner circumference of the stator 21, and is connected to the compression component 3 with the crankshaft 5.
As illustrated in FIG. 2, the stator 21 includes a core 8, the magnet wire 6, an insulating film 10, and a binding thread 11. The core 8 is a cylindrical laminate of iron plates. The magnet wire 6 is arranged so as to pass through a plurality of slots 9 that are formed in the axis direction in the core 8. Further, the magnet wire 6 is bound together with the binding thread 11. Furthermore, impregnation is applied to the magnet wire 6 with impregnating varnish 12 in order to improve its insulation performance.
The insulating film 10 is provided between the core 8 and the magnet wire 6, and between the layers of the magnet wire 6.
Conventional impregnating varnishes used in the impregnation of the magnet wire 6 include solventless varnish, such as polyester resins that include an aromatic olefin compound, represented by styrene, as a reactive diluent; epoxy resin based solvent varnish; and epoxy resin based solventless varnish. When impregnation is applied to the magnet wire 6 with such solventless varnish or solvent varnish, a large amount of solvent or volatile components of the reactive diluent volatilize during thermal curing. Accordingly, from the viewpoint of reducing environmental load, the amount of volatile components and the like volatilizing during thermal curing needs to be reduced.
Incidentally, refrigeration and air-conditioning apparatuses conventionally use chlorofluorocarbon refrigerants such as dichlorodifluoromethane (R-12) and hydrochlorofluorocarbon refrigerants such as monochlorodifluoromethane (R-22) (hereinafter, these refrigerants are referred to as “conventional refrigerants”). When conventional refrigerants are used in refrigeration and air-conditioning apparatuses, mineral oil based or alkylbenzenic based refrigerating machine oil or the like (hereinafter, referred to as “conventional refrigerating machine oil”) with low polarity are typically used.
Furthermore, from the viewpoint of preventing depletion of the ozone layer, hydrofluorocarbon refrigerants such as 1,1,1,2-tetrafluoroethane (R-134a) that does not contain any chlorine atom in its molecules (hereinafter, may also be referred to as “alternative refrigerant”) are used in refrigeration and air-conditioning apparatuses. Hydrofluorocarbon refrigerants are refrigerants with zero ozone depleting potential. When the alternative refrigerant is used in a refrigeration and air-conditioning apparatus, refrigerating machine oil based on polyalkylene glycol, ester, or ether (hereinafter, referred to as “alternative refrigerating machine oil”) that have high polarity and high compatibility with the alternative refrigerant is used.
Additionally, in recent years, from the viewpoint of preventing global warming, refrigerants are being replaced to natural refrigerants such as CO2, propane, or the like, since hydrofluorocarbon refrigerants has a large GWP (Global Warming Potential), which is the magnitude of influence on the global temperature rise. Alternative refrigerating machine oil with high polarity is also employed when a natural refrigerant is used in a refrigeration and air-conditioning apparatus.
That is, the cured varnish (impregnating varnish after thermal curing) in the hermetic vessel 1 is in an environment with a high-temperature high-pressure refrigerant system, the refrigerant system such as a conventional refrigerant/refrigerating machine oil, alternative refrigerant/refrigerating machine oil, or natural refrigerant/refrigerating machine oil. In addition, since refrigerant systems such as alternative refrigerant/alternative refrigerating machine oil and natural refrigerant/alternative refrigerating machine oil have higher polarity compared to that of the conventional refrigerant/refrigerating machine oil, when an alternative refrigerant or a natural refrigerant is used in a refrigeration and air-conditioning apparatus, degradation of the cured varnish and dissolving from the cured varnish into the refrigerant system occur. In particular, the extractability from the cured varnish is high when CO2 is used as the refrigerant.
At this time, when the impregnating varnish includes components with low polarity, the compatibility between the extract that is extracted (dissolved) from the cured varnish and the refrigerating machine oil is low. Thus, substances with low molecular weight or the like is educed and is accumulated as sludge in an expansion unit, such as a capillary tube and an expansion valve, in the refrigeration and air-conditioning cycle, resulting in clogging of the expansion unit after operating for a long period of time. Accordingly, the impregnating varnish needs to have excellent resistance to the refrigerant system, such as little deterioration suppressing deterioration of mechanical strength, low extractability to the refrigerant system, and the like.
To overcome the above problems, a known impregnating varnish has been presented. For example, “an aqueous epoxy resin emulsion containing the following dissolved and/or dispersed in water: A) at least one binder selected from a group consisting of epoxy resins and modified epoxy resins; B) at least one polyurethane-based associative thickener; and C) at least one catalyst for curing that can be produced by allowing at least one boron trifluoride complex to react with at least one compound having at least one epoxy group” (see, Patent Literature 1, for example). The known impregnating varnish disclosed in Patent Literature 1, for example, aims to reduce volatile components and the like that volatiles during thermal curing.